Stolen personal records of members from the cheating hookup site Ashley Madison surfaced on the dark web on Tuesday, according to reports. The hackers who apparently breached the site last month claimed responsibility. (AshleyMadison.com)

The 9.7-gigabyte data dump showed up on the dark web, a part of the Internet that can be viewed only through encrypted Tor browsers, Wired magazine reported. A group called "The Impact Team," the cybercriminals who hacked into the site last month, claimed responsibility.

The stolen files include names, email addresses and even sexual fantasies of members of the website with the motto "Life is short. Have an Affair" and another website, Established Men, operated by Toronto-based Avid Life Media, according to Wired.

About 15,000 .mil or .gov email addresses show up among the members' ranks, the Tech magazine reported. But those addresses may not represent users' real identities because Avid Life's signup forms don't require verification.

Company officials are investigating the hack attack and working with the Royal Canadian Mounted Police, Ontario Provincial Police, Toronto Police Services and the FBI to find out who was responsible for the breach, the company said in a statement. Ashley Madison's front page boasts of 38.8 million "anonymous members" and promises "100% discreet service" on the "SSL Secure Site."

The Impact Team wants to punish Avid Life for what they claim is a failure by the company to erase users' information from its database after the users delete their accounts, the hackers have said. The cybercriminals had threatened to expose the sites' members last month.

"We have explained the fraud, deceit, and stupidity of ALM and their members. Now everyone gets to see their data," the Impact Team said in a statement. "Keep in mind the site is a scam with thousands of fake female profiles. See Ashley Madison fake profile lawsuit; 90-95% of actual users are male. Chances are your man signed up on the world's biggest affair site, but never had one. He just tried to. If that distinction matters."

Tech experts say it will take time to comb through the data, which apparently also covers seven years of credit card transactions on the site. But Wired found one description of what a user with a Canadian government phone number listed was looking for from Ashley Madison.

The records posted Tuesday include personal details like names, email addresses and credit card transactions by about 32 million users of the hookup site, Wired magazine reported. (Gallo Images/Getty Images)

"I love it when I'm called and told I have 15 minutes to get to someplace where I'll be greeted at the door with a surprise—maybe lingerie, nakedness," the user wrote. "I like to ravish and be ravished … I like lots of foreplay and stamina, fun, discretion, oral, even willingness to experiment—*smile*."

Information security experts verified that the data dump wasn't a hoax early Wednesday after initial questions.

Internal company documents in the release, including information about Avid Life Media's servers, its PayPal accounts and its passwords, show it was a "full scale compromise," TrustedSec information security firm CEO Dave Kennedy wrote on the company's blog.

"Regardless of ethics, this is a massive data breach where attackers had full and maintained access to a large percentage of Ashley Madison's organization undetected for a long period of time," Kennedy wrote. "This dump appears to be legit. Very, very legit."

Avid Life Media said it's investigating the breach and working with law enforcement agencies, including the FBI. (Lee Jin-man/AP)

Avid Life Media officials are trying to verify the information posted on Tuesday and they'll be operating the sites while trying to remove "any information unlawfully released to the public," the company's statement said.

"This event is not an act of hacktivism, it is an act of criminality," the company said. "It is an illegal action against the individual members of AshleyMadison.com, as well as any freethinking people who choose to engage in fully lawful online activities."

"The criminal, or criminals, involved in this act have appointed themselves as the moral judge, juror, and executioner, seeing fit to impose a personal notion of virtue on all of society. We will not sit idly by and allow these thieves to force their personal ideology on citizens around the world."